architecture: update secure boot links

The TF-A repository restructured its documentation with subfolders,
change the links accordingly.

Signed-off-by: Rouven Czerwinski <rouven@czerwinskis.de>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
diff --git a/architecture/secure_boot.rst b/architecture/secure_boot.rst
index ea10f20..7c8f948 100644
--- a/architecture/secure_boot.rst
+++ b/architecture/secure_boot.rst
@@ -44,7 +44,7 @@
 directly to the manufacturer for the device you are working with to be able to
 understand how to do secure boot on their devices.
 
-.. _auth-framework.rst : https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/auth-framework.rst
+.. _auth-framework.rst : https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/design/auth-framework.rst
 .. _mbed TLS: https://github.com/ARMmbed/mbedtls.git
-.. _user-guide.rst: https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/user-guide.rst
-.. _trusted-board-boot.rst: https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/trusted-board-boot.rst
+.. _user-guide.rst: https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/getting_started/user-guide.rst
+.. _trusted-board-boot.rst: https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/design/trusted-board-boot.rst